1. Field of the Invention
The present invention relates to a variable optical element, an optical unit, and an image capturing device.
2. Description of Related Art
In a conventional optical element of which focal distance is variable, it has been proposed that a first liquid member and a second liquid member which does not mix with the first liquid member are contained in a contained in an air-tight manner; thus, an interfacial shape varies such that the focal position may be variable (see Japanese Unexamined Patent Application, First Publication No. 2001-249261). In the optical element which is used in a device which is disclosed in the Japanese Unexamined Patent Application, First Publication No. 2001-249261, the first liquid member and the second liquid member having the same specific gravities as each other are contained in a container in an air-tight manner, and an electricity is applied to an electrode which is disposed on the container. By doing this, a interfacial tension between the first liquid member and the second liquid member varies. Therefore, in a lens which is formed by the second liquid member, a diameter, a thickness, and a curvature of a bottom surface of the lens vary. By doing this, the focal distance in the above optical element varies.
Also, as far as the above optical element is concerned, it is disclosed that an aberration occurs due to an influence of gravity. Here, it should be noted that such an aberration is generated under condition that there is a difference in a density between the two liquid members and that the optical element is disposed approximately parallel with the optical axis (see Japanese Unexamined Patent Application, First Publication No. 2001-249261, and “Current Developments in Lens Design and Optical Engineering III: PROCEEDING OF SPIE, VOL. 4767, 8-9, Jul. 2002”).